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Thread: Can MDADM rebuild RAID without config file?

  1. #1
    Join Date
    Jun 2014
    Beans
    15

    Can MDADM rebuild RAID without config file?

    I have a home media server that is running Ubuntu 14 something that has 7 drives in it: a single SSD boot drive and 6 HDD drives in a RAID6 format setup using MDADM. The SSD is just the bootable OS, the MDADM configuration, and the media server software with the data on the 6 HDD drives.

    We recently lost power and found that the BIOS is not seeing the SSD drive while it is finding the other 6 drives properly. As there is no bootable drive to find, the server doesn't start. As it turns out, this is a known issue with SSD drives that lose power suddenly like in a power outage. I've been trying the various techniques to have the BIOS find the SSD drive again, but so far, they haven't worked.

    My question for this forum is, if I have to replace the SSD drive, can MDADM find the RAID6 configuration from the 6 HDDs? And if so, what commands do I run?

  2. #2
    Join Date
    Jan 2008
    Beans
    147
    Distro
    Kubuntu 18.04 Bionic Beaver

    Re: Can MDADM rebuild RAID without config file?

    Yes, it can. Install mdadm package and run 'mdadm --assemble --scan'. If everything is ok run 'mdadm --detail --scan >> /etc/mdadm/mdadm.conf' and edit the last ARRAY line in mdadm.conf you've just added to give it a permanent name e.g. /dev/md1 - by default it starts numbering md devices from 127 down and that may change. Add a line to /etc/fstab to mount it automatically. Reboot to test.

  3. #3
    Join Date
    Jun 2014
    Beans
    15

    Re: Can MDADM rebuild RAID without config file?

    Thank you for the quick reply. I'm still trying to boot off the original SSD drive which still isn't recovering while I wait for a new SSD drive to be sent. It will likely take a few days to make it here. I'll update this thread once I have it running again.

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